Its amazing how when the data support their claims, no RCT is needed. There are too many variables to truly know if masks were the only reason there was a difference in the numbers. Mask wearers, in general, would tend to be more afraid of the virus and, therefore, more careful with hand hygiene, for one. More rigorous studies have shown that masks less than N95 were ineffective for influenza, a larger microbe than covid. It would likely follow the same would be true for a virus of smaller particle size.